Passage of Treponema pallidium through membrane filters of various pore sizes.

The passage of Treponema pallidum through commercially available Millipore membrane filters of various pore sizes was examined. No microscopically detectable organisms passed through a filter with a pore diameter of 0.22 mum. As pore size was increased, progressively more organisms passed through. Motile organisms passed through filters to a greater extent than nonmotile ones; however, 22% of the motile and 50% of the nonmotile T. pallidum organisms did not pass through the largest pore diameter tested (14.0 mum). Filtration of T. pallidum suspensions through membrane filters may offer a way of separating the organisms from larger particles of debris which accompany their extraction from rabbit testicular syphilomas.